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This is part 12 of the LoRa/LoRaWAN tutorial.
In this video series different topics will be explained which will help you to understand LoRa/LoRaWAN.
It is recommended to watch each video sequentially as I may refer to certain LoRa/LoRaWAN topics explained earlier.
In this video I will explain what the basic modulation types are and what Chirp Spread Spectrum is.
Modulation means how analog or digital information are encoded onto a carrier signal.
When analog information are encoded onto a carrier signal, three modulation types can be used:
Amplitude Modulation (AM), Frequency Modulation (FM) and Phase modulation (PM).
When digital information are encoded onto a carrier signal, three modulation types can be used:
Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK) and Phase Shift Keying (PSK).
As mentioned earlier an end node has a radio module.
This radio module has a modulator which encodes information onto a carrier signal.
This modulated signal is transmitted and received by a gateway.
The gateway also has a radio module.
This radio module has a demodulator which decodes the modulated signal and extracts the information.
The communication between the end node and gateway is bidirectional which means the end node can send data to the gateway but it can also receive data from the gateway.
If a device can both transmit and receive signals this device is also called a transceiver.
LoRa end nodes and gateways are transceivers.
Amplitude Shift Keying (ASK): Only the amplitude changes
Frequency Shift Keying (FSK): Only the frequency changes
Phase Shift Keying (PSK): Only the phase changes
Besides the 3 basic modulation types there are many other modulation types.
LoRa is a proprietary spread spectrum modulation scheme that is based on Chirp Spread Spectrum modulation (CSS).
Chirp Spread Spectrum is a spread spectrum technique that uses wideband linear frequency modulated chirp pulses to encode information.
Spread spectrum techniques are methods by which a signal is deliberately spread in the frequency domain.
For example a signal is transmitted in short bursts, "hopping" between frequencies in a pseudo random sequence.
This is explained in Tutorial 11.
A chirp, often called a sweep signal, is a tone in which the frequency increases (up-chirp) or decreases (down-chirp) with time.
These chirp signals are used as carrier signals where a message is encoded on.
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